The present invention relates generally to automotive exhaust systems and, in particular, to a valve in an automotive exhaust system.
Automotive exhaust systems function to rout and treat an exhaust gas stream from an inlet connected to an internal combustion engine to an outlet to atmosphere. Exhaust systems include piping attached to the engine, and mufflers, catalytic converters, resonators and the like disposed in the piping to remove impurities and noises from the exhaust gas stream prior to the exhaust stream exiting to atmosphere. Exhaust systems function to maintain the flow of exhaust gases to atmosphere while also providing back pressure, i.e. restriction, for the engine.
With some newer engines able to switch between an eight cylinder mode and a four cylinder mode, this new powertrain option results in a high exhaust gas output mode and a low exhaust gas output mode. By varying the displacement of the engine, drastically different exhaust flow rates are produced, for example, when the engine is in eight cylinder or high output mode compared to when, for example, the engine is in a four cylinder or low output mode. Current commercially available valves in the exhaust system have dual inlet chambers containing flapper valves, which valves are passive devices that perform an open/closed operation to direct flow to a single outlet chamber. However, these passive devices are incapable of providing an adjustable restriction to exhaust gas flow due to changes in exhaust gas flow from a variable displacement engine.
It is desirable, therefore, to provide an exhaust valve assembly that is adapted to be disposed in an automotive exhaust system and is operable to maintain both flow and back pressure requirements for the exhaust system regardless of the type of engine and especially for an engine whose exhaust flows and back pressures can vary greatly due to engine cylinder deactivation.